A dynamic message sign is a sign having a message that can be changed by a user. Dynamic message signs can be used to publicly display information that can be changed. For example, dynamic message signs can be used as roadway signs to alert motorists of traffic information or they can be used as commercial signs to advertise business or product information. Dynamic message signs are typically connected to a controller for controlling the message on the sign's display. A controller is typically a computer having a communication interface for communicating with the sign.
Dynamic message signs can also be made up of multiple display units, each of which are responsible for producing part of the sign's display. In a dynamic message sign having multiple display units, the controller must communicate with each display unit in order to refresh the display. In order to communicate with the sign, the controller must recognize the configuration of the display units. Typically, a user provides the configuration information to the controller. When the configuration is changed or the controller is replaced, a user must re-enter the configuration information.